1. Field of the Invention
The present invention relates to a potassium/sodium ion sensing device applying an extended-gate field effect transistor, particularly to a potassium/sodium ion sensing device applying an extended-gate field effect transistor which uses an ion interference for mutual correction to obtain more accurate values. Therefore, the present invention can be applied to industries such as medical examinations, biomedical materials, and semiconductor device fabrications, etc.
2. Description of the Prior Art
As compared with conventional ion selective glass electrodes, at present the solid-state electrode has more advantages, such as low cost, easy miniaturization and durability, non-breakable, etc., therefore the market share is tend to ripe semiconductor integration of field effect transistor substitute for conventional glass electrode. [P. Bergveld, “Development of an ion-sensitive solid-state device for neurophysiological measurements”, IEEE Transactions on Biomedical Engineering, BME-17, pp. 70–71, 1970].
The fluid of a human body can be classified to extra-cellular and intra-cellular fluids, wherein primary ions include sodium, potassium, calcium, etc.; the balance of sodium ion and potassium ion is important particularly. In the normal condition of a human body, the concentration of sodium/potassium ions is stable, the normal value of serum potassium is 3.5–5.0 mM(avg. 4.3 mM), the normal value of serum sodium is 135–145 mM(avg. 140 mM)[pp. 847–900, Sec. 2 Examination, The Clinical Internal Medicine, BOR-SHEN HSIEH, published by Golden Name Press, 1990]. Thus, sodium is a major cation in the extra-cellular fluid of a human body, 98% ion is sodium ion in all extracellular, and 2% ion is sodium ion in all intra-cellular. The potassium and sodium ion concentration will change if a patient has kidney failure or dehydration, thus the doctor can use the unbalance condition of sodium/potassium ions to examine the disease of the human body. The determination of content of sodium/potassium ions in the human body is generally performed by polarographic method, atomic absorption spectrometry (AAS), and the like which need pre-processing and operating inconveniently. Those current commercial pH/sodium/potassium ion electrodes often have errors when used to measure the environment of interfering ion more than the measured ion (that is, the extra-cellular and intra-cellular fluids in the human body). Thus, in order to remove the interference from various ions on electrodes, it is required to measure the ions having greater effects in the solution simultaneously.
Patents related to the conventional technology are described as follows:
(1) Inventor: D. C. Chan Andy, Patent Number: U.S. Pat. No. 6,416,646; Date of patent: Jul. 9, 2002, Title: “Method of making a material for establishing solid state contact for ion selective electrodes”. This cited reference discloses a polymeric material, a methacrylamidopropyltrimethyl-ammoniumchloride (MAPTAC) or methyllmethacrylate (MMA), applied on the gate of a field effect transistor to fabricate an ion selective electrode, which is stable and reproducible, and polymeric membrane mixable with ion selective material being incorporated in a solid-state electrode; The electric charge of the polymer described in the cited reference is 2.72 mEq/g (millaequivalents/gram), and the polymeric material recited in the claims includes immobilized sites of charge opposite that of mobile ions involved in the redox couple.
(2) Inventor: Martijn Marcus Gabriel Antonisse, David Nicolaas Reinhoudt, Bianca Henriette Maria Snellink-Ruel, Peter Timmerman, Patent Nubmer: U.S. Pat. No. 6,468,406. Date of patent. Oct. 22, 2002, Title: “Anion-complexing compound, method of preparing the same, an ion-selective membrane and a sensor provided with such a compound or membrane”. This cited reference discloses the synthesis and application of an ion selective material of alkali and alkaline earth group, using organic synthesis, to prepare compounds with specific functional group; such as —NHC(X)—, —C(X)NH—, —NHC(X)NH—, wherein X includes sulfur or oxygen atom, with its specific compound structure, to achieve the effect for selecting an ion selective material of alkali and alkaline earth group; the cited reference also discloses, adding on a polymer to encapsulate an ion selective material, to prepare an extended gate ion selective electrode.
(3) Inventor: Massimo Battilotti, Giuseppina Mazzamurro, Matteo Giongo, Invent Number: U.S. Pat. No. 5,130,265. Date of patent. Dec. 21, 1989, Title: “Process for obtaining a multifunctional, ion-selective-membrane sensor using a siloxanic prepolymer”. This cited reference discloses a process, using a photocurable polymer, to achieve fixing various ion selective materials on a microelement. A claimed process of a sensing device, which using a solvent with a photoinitiator to solve silica and an ion selective material, applied to a substrate in liquid using spinning, and then exposed with appropriate ultraviolet light, after cleaned by an organic solvent, hardening the polymer by heating, and repeating the above, to obtain a sensing electrode in the same substrate, and thus making various ion field effect transistor sensing devices.
(4) Inventor: Akihiko Mochizuki, Hideyo lida, Patent Nubmer: U.S. Pat. No. 4,921,591. Date of patent. May 1, 1990, Title: “Ion sensors and their divided parts”. This cited reference discloses an ion selective membrane, includes a vinyl polymer based compound containing a hydroxyl and/or carboxyl group, fixed on an extended gate sensitive field effect transistor. In the claims, it also discloses a reference electrode arranged in the opposite side of a ion selective electrode. The ion selective electrode and reference electrode are separate. The materials of reference electrode is different with the extended gate.
(5) Inventor: Noboru Oyama, Takeshi Shimomura, Shuichiro Yamaguchi, Patent Number: U.S. Pat. No. 4,816,118. Date of patent. Mar. 28, 1989, Title: “Ion-sensitive FET sensor”. This cited reference discloses an ion selective electrode (ISFET), the gate of MOSFET is pulled out, and an ion selective membrane is added; wherein a redox layer having a redox function is provided between the isolating membrane and the ion-sensitive layer to improve operating stability and speed of response; an electrically conductive layer or a combination of a metal film and an electrically conductive layer is provided between the isolating membrane and the redox layer to further improve operating stability, the adhesion of the layers and the durability of the sensor. Also disclosed are optimum materials for use as an ion carrier employed in the ion-sensitive layer.
(6) Inventor: D. N. Reinhoudt, M. L. M. Pennings, A. G. Talma, Paten Number: U.S. Pat. No. 4,735,702. Date of patent. Apr. 5, 1988, Title: “Method of producing an ISFET and same ISFET”. This cited reference discloses: a method of modifying an oxide surface of a semi-conductor material, incorporated for example in an ISFET, in which a polymer coating is applied to the oxide surface. This cited reference also describes: using a modified polymer to fix oxide functional group to the gate of a field effect transistor or to introduce a metal complex into a polymer, and thus to achieve a product for mass production.
Furthermore, since the miniaturization of an optical ion sensor is difficult, although electrical ion sensor can use an integrated circuit process to achieve miniaturization, the sensitive potential signal is subjected to the ion movement in the solution to produce noise. In order to stabilize the potential signal or improve potential interference, generally can add a filter circuit at the back end circuit, or as the above-cited reference (1)–(6), can change the feature of polymer of the ion selective membrane. And, according to the literatures: [IUPAC, “Recommendations for nomenclature of ion-selective electrodes”, Pure and Applied Chemistry, Vol. 66, pp. 2527–2536, 1994. R. Eugster, P. M. Gehrig, W. E. Morf, U. E. Spichiger, and W. Simon, “Selectivity-modifying influence of anionic sites in neutral carrier-based membrane electrodes”, Analytical Chemistry, Vol. 63, pp. 2285–2289, 1991. M. Yanming and E. Bakker, “Determination of complex formation constants of lipophilic neutral ionophores in solvent polymeric membranes with Segmented sandwich membranes”, Analytical Chemistry, Vol. 71, pp. 5279–5287, 1999. S. Amemiya, P. Bu1hlmann, E. Pretsch, B. Rusterholz, Y. Umezawa, “Cationic or anionic Sites-selectivity optimization of ion-selective electrodes based on charged ionophores”, Analytical Chemistry, Vol. 72, pp. 1618–1631, 2000. E. Bakker, E. Pretsch, “Ion-selective electrodes based on two competitive ionophores for determining effective stability constants of ion-carrier complexes in solvent polymeric membranes”, Analytical Chemistry, Vol. 70, pp. 395–302, 1998. F. Deyhimi, “A method for the determination of potentiometric selectivity coefficients of ion selective electrodes in the presence of several interfering ions”, Talanta, Vol. 50 (5), pp. 1129–1134, 1999. E. Bakker, “Origin of anion response of solvent polymeric membrane based silver ion-selective electrodes”, Sensors and Actuators B, Vol. 35 (1–3), pp. 20–25, 1996. P. Kane, D. Diamond, “Determination of ion-selective electrode characteristics by non-linear curve fitting”, Talanta, Vol. 44, pp. 1847–1858, 1997], ion interference is: when the solution to be tested contains other ion not to be tested, the amount of the ion not to be tested can affect the output potential, so the output potential can not indicate correct concentration of the ion to be tested. However, using polymer for fixing is a special subject, different polymers will affect the ion diffusivity and ionophore encapsulatement [C. P. Hauser, W. L. D. Chiang, A. W. Graham, “A potassium ion selective electrode with valinomycin based poly (vinyl chloride) membrane and a poly (vinyl ferrocene) solid contact”, Analytical Chimica Acta., Vol. 302, pp. 241–248, 1995. B. Andrey, A. Nataliya, M. Javier, D. Carlos, “Optimization of photocurable polyurethane membrane composition for ammonium ion sensor”, Journal of Electrochemical Soc., Vol. 144 (2), pp. 617–621, 1997. Y. H. Lee, A. H. Hall Elizabeth, “Methacrylate-acrylate based polymers of low plasticiser cont for potassium ion-selective membranes” Analytical Chemica Acta., Vol. 324, pp. 47–56, 1996. B. Jundrey, A. Nataliya, M. Javier, D. Carlos, A. Salvador, B. Jordi “Photocureable polymer matrices for potassium-sensitive ion selective electrode membranes” Analytical Chemistry, Vol. 67, pp. 3589–3595, 1995Yook-Heng Lee, A. H. Elizabeth, “Assessing a photocured self-plasticised acrylic membrane recipe for Na and K ion selective electrodes”, Analytica Chimica Acta, Vol. 443, pp. 25–40, 2001. K. J. Shinichi, M. S. Arakawa, S. Michiko, O. Tetsuya, S. lkuo, “Flow injection analysis of potassium using an all-solid-state potassium selective electrode as a detector”, Talanta, Vol. 46, pp. 1293–1297, 1998. P. C. Pandey, R. Prakash, “Polyiudole modified potassium ion sensor using dibenzo-18-crown-6 mediated PVC matrix membrane”, Sensors and Actuators B, Vol. 46, pp. 61˜65, 1998. M. J. Roger, P. J. S. Barbeiva, A. F. B. Sene, N. R. Stradiotto, “Potentiometria determination of potassium cations using a nickel(II)hexacyanofereate-modified electrode”, Talanta, Vol. 49, pp. 271–275, 1999]. The amount of negative charge ionophore and additive influence the potentiometric selectivity coefficient in potassium/sodium ion electrodes [R. Eugster, P. M. Gehrig, W. E. Morf, U. E. Spichiger, and W. Simon, “Selectivity-modifying influence of anionic sites in neutral carrier-based membrane electrodes”, Analytical Chemistry, Vol. 63, pp. 2285–2289, 1991. S. Amemiya, P. Bu1hlmann, E. Pretsch, B. Rusterholz, Y. Umezawa, “Cationic or anionic Sites-selectivity optimization of ion-selective electrodes based on charged ionophores”, Analytical Chemistry, Vol. 72, pp. 1618–1631, 2000], in a potassium/sodium ion sensor, if the ionosphere or electronegative additive is larger than a certain amount, the positive charge of other ions to be tested will be affected by electronegativity. Addressing to the problem of potential interference, the International Union of Pure and Applied Chemistry (IUPAC) had recommended the potential interference parameters of a potentiometric sensor [IUPAC, “Recommendations for nomenclature of ion-selective electrodes”, Pure & Applied Chemistry, Vol. 66, pp. 2527–2536, 1994], potantiometric selectivity coefficient can input The Nikolsky-Eisenman equation to obtain more accurate potassium/sodium ion concentration in practice.
Accordingly, it can be seen that the above-described conventional technique still has many drawbacks, are not designed well, and thus need to be improved.
In view of disadvantages derived from the above-described conventional techniques, the present inventor had devoted to improve and innovate, and, after studying intensively for many years, developed successfully a potassium/sodium ion sensing device applying an extended-gate field effect transistor according to the invention.